The Study On Thermal Performance Of Parabolic Trough Heat Receiver

As the fossil energy is drying up day by day, the environmental pollution and ecological destruction problem caused by fossil energy become more and more apparent, people pay more attention to the exploitation of solar energy, bio-mass energy, wind energy, and other renewable energy.Solar power generation technology is a kind of way to develop and use solar energy, as the only commercial solar thermal power generation technology at the moment, it has been used widely. As the key component in solar power generation system, the heat performance and reliability of vacuum receiver affect the initial investment and generating cost of solar power generation systems directly. Due to the inconsistency of expansion coefficient between metal tube and glass tube, when the receiver operating under high temperature, different hot deformation lead to biggish thermal stress at the sealing between metal tube and glass tube, And the thermal stress changes with the solar radiation intensity, which can cause the seal failure easily, or glass tube broken. Vacuum failure and glass broken are the main factors of economic losses in solar thermal power plant, so the sealing technology between metal tube and glass tube become a hot spot of research at home and abroad.In different environmental conditions, the obtain of parabolic receiver thermal performance is the foundation of researching and developing new sealing technology between metal tube and glass tube, so this paper focuses on the research of thermal performance by combining theoretical analysis with experimental study, and describes a method to monitor vacuum rapidly and accurately with glass temperature, and basis on the theoretical analysis, the test set of the thermal loss of the CPC also carried out.This paper acquires the following major results.1. Considering the heat balance of receiver, the formulation of the relation between glass temperature and heat loss is deduced, and link to the correlation formula of PTR70, the glass temperature range is expressed with different wind speed, ambient temperature, solar radiation intensity and working fluid temperature when PTR70 parabolic trough receiver in excellent working condition. With the vacuum failure and glass broken, the heat loss of receiver is discussed. The study finds that, The environment change influences the glass temperature obviously, while the heat loss of receiver influences less comparatively; the working fluid temperature is the main influence on the heat loss of PTR70; the glass temperature and heat loss are increased significantly when the vacuum failure, the glass temperature is 138.65℃When the wind speed is 2m/s, which is above 100℃than the case of vacuum with the same condition, and the heat loss as many as 1046.01 W/m, which approximates 7 times compares to the case of normal operation, and the influence of hydrogen to glass temperature and heat loss is smaller than the case when the air leak into annular slightly; once the glass is broken, the heat transfer will take place between metal pipe and the environment, under the same condition, the heat loss is 16 times as much as the annular keep vacuum.2. The Compound Parabolic Concentrator (CPC) has been developed. The thermal performance test experimental research of receiver is carried out at Yangwayao primary school, Gaolan County, Lanzhou. According to the experiment results, the temperature curves varying with time are obtained with the CPC collector under the sun and in different weather condition; during the experiment, the working fluid temperature increases 7.41℃/ h in sunny day, and increases 4.43℃/ h in cloudy day. Then use the method which is measure the heat loss with glass temperature, the receiver heat loss at different times is calculated.The subject innovation points:1. The study suggests judge vacuum of receiver by glass temperature, and reveals the influence of the vacuum to thermal properties.2. The thermal performance of receiver for breaking vacuum is obtained by experiment in Lanzhou area.As the key component in solar power generation system, the vacuum receiver affects the initial investment and generating cost of parabolic trough power system directly. The thermal performance and reliability mainly depends on the sealing method between the metal tube and glass tube,and the thermal performance of parabolic receiver in different environmental conditions is the foundation of sealing technology between the metal tube and glass tube. This subject studies the thermal performance of receiver in Lanzhou area by the method of theoretical analysis and experimental research,the results will provide the first-hand datas for the wide application of solar power generation technology in northwestern China, and provide the reference to master the sealing technology of parabolic trough receiver between the metal tube and glass tube ,and the research of new method.